This application is a 35 USC 371 application of PCT/DE 00/03899 filed on Nov. 8, 2000.
1. Field of the Invention
The invention relates to the industrial field of controlling fuel quantities in large diesel engine applications, in which longer valve strokes at higher flow cross sections are required on the one hand and smaller injection quantities at high rpm are required on the other.
2. Description of the Prior Art
From the prior art, fast-switching valves in which fast-switching magnets are provided are known for passenger car and truck applications. The switching times attainable with fast-switching magnets can be attained especially in applications in which small flow cross sections for the fuel are needed and the valve strokes are in particular shorter than about 0.3 mm. In large diesel engines, which are used in maritime applications for instance or in armored vehicles for military purposes, longer valve strokes must be achieved, since the fuel quantities required are greater. At longer valve strokes and high fuel quantities, however, the advantages of shorter switching times that are attainable with electrically triggerable magnets vanish, since the magnets are capable of bringing only limited closing forces to bear, forces that are exceeded in large diesel engine applications. On the other hand, for applications in large diesel engines, 2/2-way valves are of only limited use. These larger-sized 2/2-way valves furnish the larger injection quantities required at lower rpm and also bring the requisite high closing forces to bear on the control edges of the control slide. On the other hand, the switching times of such large-sized 2/2-way valves are longer, since the masses in motion on the valve, armature plate and closing body entail greater forces of inertia. Furthermore, the valve strokes are longer, which makes the switching times longer as well.
In the higher rpm range, large diesel engines require smaller metered fuel quantities, which can be achieved only with difficulty with sluggish 2/2-way valves, because of their longer switching times. Fast-switching magnet valves, conversely, do not bring to bear the requisite high closing forces for sealing off the control edges; on the other hand, with this type of valve, smaller fuel quantities can indeed be attained.
With a valve according to the invention, the advantages of longer stroke paths and longer switching times at higher flow cross sections of the 2/2-way valve can advantageously be combined with the shorter switching times attainable with magnet valves and smaller metered fuel quantities at higher rpm. With the control unit, the two actuating devices that trip the adjusting motion of the control part can be triggered individually and make it possible for the suction chamber surrounding the control part to enter into communication with a pump chamber acting as a reservoir, or for the pump chamber to be disconnected from the high-pressure line
By making the diameter of the cylinder and the closing body different in the control part embodied movably in the housing, it is possible by means of the pressure acting on the larger diameter of the closing body in cooperation with the energy accumulator on the return side, to achieve a defined end of pumping out of the pump chamber, which pump chamber can be made to communicate with the high-pressure line again by means of impact of the closing body with the stop assigned to it in the bore in the housing.
In the control part, there is a through bore which via openings in the control part communicates with respective hollow chambers that receive the energy accumulators. The through bore carries excess fuel back to the fuel tank via the return line; an overflow line is assigned to the suction chamber surrounding the control part in the housing of the control unit, and at high system pressures that occur, this overflow linexe2x80x94protected by a check valve disposed upstream of the tankxe2x80x94protects the control unit from damage.